Line support insulator with discharge means



Aug. 29, 1967 w, HARMON 3,339,116

LINE SUPPORT INSULATOR WITH DISCHARGE MEANS Filed March 8, 1965 2 Sheets-Sheet l IN VEN TOR. ROBE R T W. HA RMON "Z11 pm ATTORNEY Aug. 29, 1967 w. HARMON LINE SUPPORT INSULATOR WITH DISCHARGE MEANS Filed March 8, 1965 2 Sheets-Sheet 2 v Ali/471.271

INVENTOR. ROBERT W. HARM ATTORNEY United States Patent Ofitice 3,33-9,l l6 Patented Aug. 29, 1967 assignor to The Mansfield, Ohio, a corporation This invention relates to insulators and insulating devices for electric line conductors. In the art pertaining to overhead lines, it is known that insulators may flash over as a result of an accumulation of contaminants on the exterior surface of the insulator to produce leakage currents over the insulator. Particularly, leakage current flashovers may be produced although the insulator has a substantially higher insulating capability than is required by the line voltage as such. As a consequence of the flashover, the circuit protector may be operated or the insulator may be destroyed.

Arrangements of valve resistors in series with an insulator for discharging overvoltage induced flashovers are descrebide in United States Patent 3,328,640, issued June 27, 1967, to J. W. Kalb. The present invention contemplates useful combinations of insulating bodies with valve resistors for suppressing overvoltage induced flashovers and leakage current induced flashovers.

According to the invention, there is provided a combined insulator and discharge device in which series connected valve resistors are incorporated on the interior of an insulator adapted for supporting a line conductor from a pole or tower structure. The mechanical arrangement .of the valve resistors is such that the parts of the insulator constitute interconnecting and terminal means for the resistors, and the mounting bolt for the insulator is utilized as a terminal for a ground lead from the insulating device to earth.

An important feature of the insulating device of the invention is that insulators for use in regions having substantial atmospheric pollutants which function as contaminants when deposited on electric insulators need not be substantially larger than insulating devices designed for normal contaminant-free locations. Another feature of the invention is the reduction in service outages in line operation.

The invention will be more clearly understood by reference to the following detailed specification and claims, taken in connection with the appended drawings in which:

FIG. 1 is a view of a line conductor and an exterior view of a combined insulator and resistive discharge device in accordance with the invention;

FIG. 2 is a vertical sectional view of the insulating device of FIG. 1;

FIG. 3 is an exterior view of another combined line support insulator and discharge device in accordance with the invention; and

FIG. 4 is a vertical section of the device of FIG. 3.

As is shown in FIG. 1, an insulating device of the invention supports a line conductor 11, comprising one conductor of a distribution line of the like, from a cross arm 12 or other structural member. The insulating device 10 is secured to the cross arm 12 by a bolt 13 which functions as a support bracket and as an electrical terminal for the device and is connected to a ground 14 by a ground lead 15. The conductor 11 is carried at the top of an insulator 16 which comprises the body or housing of the insulating device 10, and is secured to the insulator by a tie wire 17, in accordance with the known line construction practice.

The insulator 16 is constructed as a hollow member, of porcelain or other structural insulating material, with an interior opening 18 and flanges 19 extending circumferentially about the exterior of the member. The top of the insulator is formed with a head flange 20 and a groove 21 to receive the conductor 11 and the tie wire 17. The lower extremity of the insulator 16 is received in a metal base 22 and is secured to the base by means such as a concrete bond 23. The bolt 13 extends through the base 22 and is insulated from the base by means of a collar 24 aranged coaxially between the bolt 13 and the base. The collar 24 may be constructed as an annular part of porcelain or other structural insulating material.

Two discharge resistors 25 and 26 are arranged in the opening 18 of the insulator 16 and are connected to form an electrical series circuit between the base 22 and the bolt 13. The resistor 25 is constructed .as a tubular body and is arranged coaxially within the insulator 16 and coaxially about the collar 24 with the end face of the resistor body in mechanical and electrical contact with the interior surface of the base 22. The resistor 26 is constructed as a solid cylindrical body and is arranged coaxially within the resistor 25 with the end face of the resistor body in mechanical and electrical contact with the head of the bolt 13. The resistors 25 and 26 are mechanically positioned and electrically connected by a spring clip 27 which extends between the upper ends of the bodies of the resistors and the interior surface of the insulator 16.

The resistors 25 and 26 are each constructed as a rigid body of silicon carbide in a ceramic or other binder, as is known in the art. The resistors are constituted with a decreasing resistance function of increasing current magnitude, referred to herein as a valve resistor. Non-linear resistors having a voltage exponent in the range from 5 to 7 are preferred, although resistors having linear or other non-linear characteristics may be utilized in the practice of the invention, as described in United States Patent 3,328,640.

The insulator and discharge device 10 comprises a series discharge circuit from the base 22, through the resistor 25, through the clip 27, longitudinally through the resistor 26 and the bolt 13 to the ground lead 15. With this arrangement, any electrical conductive paths which are established between the conductor 11 and the base 22, as by leakage currents over the exterior surface of the in sulator 16 or are discharges from the conductor 11 or tie wire 17 to the base 22, are transmitted to ground through a resistive path whose resistance is a function of the discharge current. Accordingly, there is no cumulative leakage current process such as would lead to destruction of the insulator 16 in the absence of the series discharge resistors 25 and 26.

The device 10 functions to discharge overvoltage induced flashovers as is described in United States Patent 3,328,640.

The combined insulator and discharge device 30 of FIG. 3 and FIG. 4 comprises an insulator 31, a base 32, discharge resistors 33 and 34, a clip 35, and attachment bolt 36, as in the device 10 of FIG. 1 and FIG. 2. The device 30 is, however, constituted with a collar or insulating member 37 which insulates the resistor 34 and bolt 36 from the base 32 and resistor 33, performing the same function as the collar 24 in the device 10. The collar 37 extends between the resistors 33 and 34, in the part 38 thereof, to electrical-1y insulate the resistors 33 and 34 along the entire length thereof, and over the exterior of the bolt 36, in the part 39 thereof, along substantially the entire length of the bolt to electrically insulate the bolt from the cross arm 40.

The part 38 of the collar 37 insulates the two resistors 33 and 34 and prevents arcing, particularly at the lower portion of' the resistors. The bolt 36, collar 37, and resistor 34 may be constituted as a unitary part in which the collar 37 is constituted by a layer or coating of structural organic insulating material, or ceramic material, porcelain, or the like, over the bolt 36 and resistor 34. A good electrical and mechanical contact between the resistor 34 and the bolt 36 may be insured by metallized coating applied on the end surface of the resistor 34. Alternately, the collar 37 may be formed by molding the parts with an organic insulating material, epoxy resin, or the like, uniting the bolt 36 and the resistor 34, or the bolt 36, resistor 34, and resistor 33 in a single part.

The part 3 of the collar 37 comprises an insulating means for preventing fiashover from the base 32 or the line conductor to the bolt 36 to bypass the resistors 33 and 34. The collar 37 prevents such flashover and insures the functioning of the resistors 33 and 34 in a discharge path through a ground lead 41 to earth 42.

The insulating function of the collar 37 is augmented by the cross arm 40 which extends outwardly from and beyond the radial extremities of the base 32 in all directions, and is constituted as a body of insulating material such as impregnated wood, glass fiber reinforced epoxy resin, or the like.

A conductor holder or cap 43 at the top extremity of the insulating body 31 has the peripheral extremity 44 arranged to cooperate with the peripheral extremity 45 of the base 32 to constitute an electrode means and define a discharge path between the line conductor 46 and the base 32 of the device.

It is to be understood that the foregoing description is not intended to restrict the scope of the invention and that various rearrangements of the parts and modifications of the design may be resorted to. The following claims are directed to combinations of elements which embody the invention or inventions of this application.

I claim:

1. Line support apparatus adapted for use as a unitary insulator and discharge means for a line conductor, comprising an insulator constituted as an elongate hollow insulating body, a metal base at one extremity of the body, and a head at the remaining extremity of the body, the head including means for receiving and securing a line conductor and the base comprising a metal part comprising one terminal of discharge paths along and across the exterior surface of the insulating body from the line conductor, discharge means comprising a resist-or received in the opening in the said insulator, having one terminal thereof electrically connected to the said base, and terminal means comprising a metal terminal part extending through the said base and electrically connected to the remaining terminal of the said resistor, and means for securing the said insulator and base to a structural support member.

2. Line support apparatus in accordance with claim 1, in which the discharge resistor is constituted as a tubular part having one extremity thereof engaged with a metal base member at an end of the insulating body and the remaining extremity of the resistor body positioned by a spring metal clip received between the resistor and the insulating body at the remaining end thereof.

3. Line support apparatus in accordance with claim 2, in which the discharge means named in claim 1 is constituted by two series-connected resistors, the second resistor comprising an elongate body received within the tubular part constituting a first resistor, the second resistor having one extremity thereof mechanically and electrically engaged with the terminal means, the remaining extremity thereof mechanically and electrically engaged with the said clip for positioning the said second resistor and electrically connecting the said resistor in series with the first-named resistor.

4. Line support apparatus in accordance with claim 2, in which the said terminal comprises a mounting means for the said insulator.

5. In combined means for supporting a line conductor, in combination, an insulator comprising an insulating body having an interior opening from one, extremity thereof, means at the remaining extremity of the insulating body for holding a line conductor exteriorly of the body, means for supporting the insulating body including a metal base part extending transversely across the opening and peripherally about the insulating body at the said one extremity of the insulating body comprising one terminal of discharge paths along and across the exterior surface of the insulator, a valve resistor arranged in the opening in the insulating body, a metal support bracket and means electrically insulating the said bracket from the said metal base part, and means connecting the valve resistor from the said metal base part to the metal bracket and comprising a non-linear discharge circuit for ground currents due to discharges over or about the insulator from the line conductor to the base part, the support bracket comprising a terminal means for connection to ground.

6. Line support apparatus in accordance with claim 5, in which the support bracket comprises a bolt fastener extending through the base part from the interior of the insulating body to the exterior, a collar of structural insulating material coaxial with the said bolt fastener insulating the bolt fastener from the base, and the valve resistor comprises two parts, one engaged with the head of the bolt fastener and the other engaged with the base part.

7. Line support apparatus in accordance with claim 6, in which the two parts of the valve resistor are coaxially arranged, the collar extends between two resistors within the insulating body and over the exterior. of the bolt fastener, exteriorly of the insulating body, for a suflicient distance to prevent flashover from the base to the bolt fastener.

8. Line support apparatus in accordance with claim 7 and, in combination therewith, a structural member supporting the insulating body and base part, the bolt fastener extending through the structural member and holding the base part on the member, and the structural member being constructed of insulating material and extending radially beyond the base part for insulating the bolt fastener from the base part.

References Cited UNITED STATES PATENTS 1,763,196 6/1930 Slepian 317-72 MILTON O. HIRSHFIELD, Primary Examiner. J. D. TRAMMELL, Assistant Examiner. 

1. LINE SUPPORT APPARATUS ADAPTED FOR USE AS A UNITARY INSULATOR AND DISCHARGE MEANS FOR A LINE CONDUCTOR, COMPRISING AN INSULATOR CONSTITUTED AS AN ELONGATE HOLLOW INSULATING BODY, A METAL BASE AT ONE EXTREMITY OF THE BODY, AND A HEAD AT THE REMAINING EXTREMITY OF THE BODY, THE HEAD INCLUDING MEANS FOR RECEIVING AND SECURING A LINE CONDUCTOR AND THE BASE COMPRISING A METAL PART COMPRISING ONE TERMINAL OF DISCHARGE PATHS ALONG AND ACROSS, THE EXTERIOR SURFACE OF THE INSULATING BODY FROM THE LINE CONDUCTOR, DISCHARGE MEANS COMPRISING A RESISTOR RECEIVED IN THE OPENING IN THE SAID INSULATOR, HAVING ONE TERMINAL THEREOF ELECTRICALLY CONNECTED TO THE SAID BASE, AND TERMINAL MEANS COMPRISING A METAL TERMINAL PART EXTENDING THROUGH THE SAID BASE AND ELECTRICALLY CONNECTED TO THE REMAINING TERMINAL OF THE SAID RESISTOR, AND MEANS FOR SECURING THE SAID INSULATOR AND BASE TO A STRUCTURAL SUPPORT MEMBER. 